Why I chose SX50HS over Panasonic FZ200. I have not tested FZ200, SLR Revo doesn't have a demo unit for me to play with.
Main advantages of SX50HS (based on my personal needs)
1. 1200mm vs 600mm (there is a signficiant difference especially if you are going to crop)
2. I am a Canon user, so I am comfortable with the layout and the OS, layout is similar to G1X, OS is the same.
3. More importantly it shares the same battery as G1X, so I can just use the spare batteries i have for G1X on SX50 HS. Furthermore both are canon, so I can also use the same accessories such as wireless remote, etc. If I get the panasonic I have to spend extra money on accessories.
4. From reviews such as ephotozine, photography blog, Canon's sensor is better in my opinion. In terms of ISO performance, Canon is more than 1 stop, perhaps two stops better than Panasonic. Therefore in my opinion SX50 is not too disadvantageous despite having more than 2 stops slower at the telephoto end. But Panasonic has the edge of shooting fast action under low light situation due to the superb f2.8 throughout the range.
Therefore to me being able to reach a subject closer and better framing is more important than having a f2.8. So I chose SX50HS in the end.